Modern television receivers and other video display devices are marketed in an environment which is highly competitive both as to cost and technical excellence. Consequently, it is very important to provide various functions with the least costly techniques. It continues to be desirable to provide television receivers with tuners for reception of radio-frequency signals, as from an antenna or a cable television system. In addition, many television receivers are fitted with video input ports for accepting various forms of baseband analog video such as S-video, RGB, or composite video. These inputs make it convenient to display the video from sources such as video cameras.
A Digital Visual Interface (DVI) has been developed by the Digital Display Working Group, Attn. DDWG Administrator, M//s JF3-362, 2111 NE 25th Avenue, Hillsboro, Oreg. 97124-5961. The DVI specification is available on-line at www.ddwg.org, and is directed toward a high-speed digital connection for visual data. It would be desirable to provide television receivers and monitors with the additional capability accepting and processing DVI video, to allow DVI video, as from video disk players, to be viewed. Among the products which are available for use with the DVI interface is an integrated-circuit DVI receiver/CRT controller, which converts DVI signals into analog video and 2H synchronizing signals. This integrated-circuit DVI receiver is type SiI907 or Sil 907, manufactured by Silicon Image, Inc., of Sunnyvale, Calif. It should be noted that “2H” represents a frequency equal to twice the standard NTSC horizontal frequency of about 15,734 Hz.
For cost and marketing reasons, not all television receivers can be fitted with DVI receivers. One inexpensive way to make a variety of television receivers is to use a common printed-circuit board for the main processing portion of all the television receivers of a group of related receivers, and to simply “leave out” the DVI receiver from those printed-circuit boards which are destined for use in low-priced television receivers. The placement of electrical components on a printed-circuit board is known as “population,” and while “depopulation” strictly speaking might suggest actual removal of a component, it can also be applied to intentional failure to place a given component in the board during assembly. Thus, one way to make a given model of a television receiver is to have a common printed circuit board for a processing portion, and to either populate or depopulate the board with the DVI receiver, in accordance with the desired subset of the model.
Many television receivers include microprocessor-based controllers. In order for the various subsets of a given model to operate, the microprocessor or controller must know whether a particular component, such as the DVI receiver, is installed or not installed, so that appropriate control can be effectuated. If the DVI receiver is installed, the microprocessor may also need to know if DVI video is presently or currently applied to the installed DVI circuitry.